func slice_slice(L *lua.State) int {
	slice, _ := valueOfProxy(L, 1)
	i1, i2 := L.ToInteger(2), L.ToInteger(3)
	newslice := slice.Slice(i1, i2)
	makeValueProxy(L, newslice, SLICE_META)
	return 1
}

func callGoMethod(L *lua.State, name string, st reflect.Value) {
	ret := st.MethodByName(name)
	if !ret.IsValid() {
		fmt.Println("whoops")
	}
	L.PushGoFunction(GoLuaFunc(L, ret))
}

func slice__newindex(L *lua.State) int {
	slice, t := valueOfProxy(L, 1)
	idx := L.ToInteger(2)
	val := LuaToGo(L, t.Elem(), 3)
	slice.Index(idx - 1).Set(valueOf(val))
	return 0
}

func GoLua(L *lua.State) int {
	go func() {
		LT := L.NewThread()
		L.PushValue(1)
		lua.XMove(L, LT, 1)
		res := LT.Resume(0)
		for res != 0 {
			if res == 2 {
				emsg := LT.ToString(-1)
				fmt.Println("error", emsg)
			}
			ch, t := valueOfProxy(LT, -2)

			if LT.ToBoolean(-1) { // send on a channel
				val := valueOf(LuaToGo(LT, t.Elem(), -3))
				ch.Send(val)
				res = LT.Resume(0)
			} else { // receive on a channel
				val, ok := ch.Recv()
				GoToLua(LT, t.Elem(), val)
				LT.PushBoolean(ok)
				res = LT.Resume(2)
			}
		}
	}()
	return 0
}

func makeValueProxy(L *lua.State, val reflect.Value, proxyMT string) {
	rawptr := L.NewUserdata(uintptr(unsafe.Sizeof(ValueProxy{})))
	ptr := (*ValueProxy)(rawptr)
	ptr.value = val
	ptr.t = val.Type()
	lua.LGetMetaTable(L, proxyMT)
	L.SetMetaTable(-2)
}

func struct__newindex(L *lua.State) int {
	st, t := valueOfProxy(L, 1)
	name := L.ToString(2)
	if t.Kind() == reflect.Ptr {
		st = st.Elem()
	}
	field := st.FieldByName(name)
	val := LuaToGo(L, field.Type(), 3)
	field.Set(valueOf(val))
	return 0
}

// GoLuaFunc converts an arbitrary Go function into a Lua-compatible GoFunction.
// There are special optimized cases for functions that go from strings to strings,
// and doubles to doubles, but otherwise Go
// reflection is used to provide a generic wrapper function
func GoLuaFunc(L *lua.State, fun interface{}) lua.GoFunction {
	switch f := fun.(type) {
	case func(*lua.State) int:
		return f
	case func(string) string:
		return func(L *lua.State) int {
			L.PushString(f(L.ToString(1)))
			return 1
		}
	case func(float64) float64:
		return func(L *lua.State) int {
			L.PushNumber(f(L.ToNumber(1)))
			return 1
		}
	default:
	}
	var funv reflect.Value
	switch ff := fun.(type) {
	case reflect.Value:
		funv = ff
	default:
		funv = valueOf(fun)
	}
	funt := funv.Type()
	targs, tout := functionArgRetTypes(funt)
	return func(L *lua.State) int {
		var lastT reflect.Type
		isVariadic := funt.IsVariadic()
		if isVariadic {
			lastT = targs[len(targs)-1].Elem()
			targs = targs[0 : len(targs)-1]
		}
		args := make([]reflect.Value, len(targs))
		for i, t := range targs {
			val := LuaToGo(L, t, i+1)
			args[i] = valueOf(val)
		}
		if isVariadic {
			n := L.GetTop()
			for i := len(targs) + 1; i <= n; i++ {
				val := valueOf(LuaToGo(L, lastT, i))
				args = append(args, val)
			}
		}
		resv := funv.Call(args)
		for i, val := range resv {
			GoToLua(L, tout[i], val)
		}
		return len(resv)
	}
}

func struct__index(L *lua.State) int {
	st, t := valueOfProxy(L, 1)
	name := L.ToString(2)
	est := st
	if t.Kind() == reflect.Ptr {
		est = st.Elem()
	}
	ret := est.FieldByName(name)
	if !ret.IsValid() { // no such field, try for method?
		callGoMethod(L, name, st)
	} else {
		GoToLua(L, ret.Type(), ret)
	}
	return 1
}

// copy a Go slice to a Lua table
func CopySliceToTable(L *lua.State, vslice reflect.Value) int {
	if vslice.IsValid() && vslice.Type().Kind() == reflect.Slice {
		n := vslice.Len()
		L.CreateTable(n, 0)
		for i := 0; i < n; i++ {
			L.PushInteger(i + 1)
			GoToLua(L, nil, vslice.Index(i))
			L.SetTable(-3)
		}
		return 1
	} else {
		L.PushNil()
		L.PushString("not a slice!")
	}
	return 2
}

// look up a Lua value by its full name. If idx is 0, then this name
// is assumed to start in the global table, e.g. "string.gsub".
// With non-zero idx, can be used to look up subfields of a table
func Lookup(L *lua.State, path string, idx int) {
	parts := strings.Split(path, ".")
	if idx != 0 {
		L.PushValue(idx)
	} else {
		L.GetGlobal("_G")
	}
	for _, field := range parts {
		L.GetField(-1, field)
		L.Remove(-2) // remove table
	}
}

func copyMapToTable(L *lua.State) int {
	vmap := valueOf(unwrapProxy(L, 1))
	if vmap.IsValid() && vmap.Type().Kind() == reflect.Map {
		n := vmap.Len()
		L.CreateTable(0, n)
		for _, key := range vmap.MapKeys() {
			GoToLua(L, nil, key)
			GoToLua(L, nil, vmap.MapIndex(key))
			L.SetTable(-3)
		}
		return 1
	} else {
		L.PushNil()
		L.PushString("not a map!")
	}
	return 2
}

// copy a Go map to a Lua table
func CopyMapToTable(L *lua.State, vmap reflect.Value) int {
	if vmap.IsValid() && vmap.Type().Kind() == reflect.Map {
		n := vmap.Len()
		L.CreateTable(0, n)
		for _, key := range vmap.MapKeys() {
			val := vmap.MapIndex(key)
			GoToLua(L, nil, key)
			GoToLua(L, nil, val)
			L.SetTable(-3)
		}
		return 1
	} else {
		L.PushNil()
		L.PushString("not a map!")
	}
	return 2
}

func slice__index(L *lua.State) int {
	slice, _ := valueOfProxy(L, 1)
	if L.IsNumber(2) {
		idx := L.ToInteger(2)
		ret := slice.Index(idx - 1)
		GoToLua(L, ret.Type(), ret)
	} else {
		name := L.ToString(2)
		switch name {
		case "Slice":
			L.PushGoFunction(slice_slice)
		default:
			fmt.Println("unknown slice method")
		}
	}
	return 1
}

func channel_send(L *lua.State) int {
	fmt.Println("yield send")

	L.PushValue(2)
	L.PushValue(1)
	L.PushBoolean(true)
	return L.Yield(3)
	//~ ch,t := valueOfProxy(L,1)
	//~ val := valueOf(LuaToGo(L, t.Elem(),2))
	//~ ch.Send(val)
	//~ return 0
}

func CopyTableToStruct(L *lua.State, t reflect.Type, idx int) interface{} {
	if t.Kind() == reflect.Ptr {
		t = t.Elem()
	}
	s := reflect.New(t) // T -> *T
	ref := s.Elem()
	L.PushNil()
	if idx < 0 {
		idx--
	}
	for L.Next(idx) != 0 {
		key := L.ToString(-2)
		f := ref.FieldByName(key)
		if f.IsValid() {
			val := valueOf(LuaToGo(L, f.Type(), -1))
			f.Set(val)
		}
		L.Pop(1)
	}
	return s.Interface()
}

func channel_recv(L *lua.State) int {
	fmt.Println("yield recv")

	L.PushValue(1)
	L.PushBoolean(false)
	return L.Yield(2)
	//~ ch,t := valueOfProxy(L,1)
	//~ L.Yield(0)
	//~ val,ok := ch.Recv()
	//~ GoToLua(L,t.Elem(),val)
	//~ L.PushBoolean(ok)
	//~ L.Resume(0)
	//~ return 2
}

func main() {
	var L *lua.State
	L = lua.NewState()
	L.OpenLibs()

	rawptr := L.NewUserdata(uintptr(unsafe.Sizeof(Userdata{})))
	var ptr *Userdata
	ptr = (*Userdata)(rawptr)
	ptr.a = 2
	ptr.b = 3

	fmt.Println(ptr)

	rawptr2 := L.ToUserdata(-1)
	ptr2 := (*Userdata)(rawptr2)

	fmt.Println(ptr2)
}

// return the Lua table at 'idx' as a copied Go slice. If 't' is nil then the slice
// type is []interface{}
func CopyTableToSlice(L *lua.State, t reflect.Type, idx int) interface{} {
	if t == nil {
		t = reflect.TypeOf(tslice)
	}
	te := t.Elem()
	n := int(L.ObjLen(idx))
	slice := reflect.MakeSlice(t, n, n)
	for i := 1; i <= n; i++ {
		L.RawGeti(idx, i)
		val := LuaToGo(L, te, -1)
		slice.Index(i - 1).Set(valueOf(val))
		L.Pop(1)
	}
	return slice.Interface()
}

// return the Lua table at 'idx' as a copied Go map. If 't' is nil then the map
// type is map[string]interface{}
func CopyTableToMap(L *lua.State, t reflect.Type, idx int) interface{} {
	if t == nil {
		t = reflect.TypeOf(tmap)
	}
	te, tk := t.Elem(), t.Key()
	m := reflect.MakeMap(t)
	L.PushNil()
	if idx < 0 {
		idx--
	}
	for L.Next(idx) != 0 {
		// key at -2, value at -1
		key := valueOf(LuaToGo(L, tk, -2))
		val := valueOf(LuaToGo(L, te, -1))
		m.SetMapIndex(key, val)
		L.Pop(1)
	}
	return m.Interface()
}

// Convert a Lua value 'idx' on the stack to the Go value of desired type 't'. Handles
// numerical and string types in a straightforward way, and will convert tables to
// either map or slice types.
func LuaToGo(L *lua.State, t reflect.Type, idx int) interface{} {
	var value interface{}

	switch t.Kind() {
	// various numerical types are tedious but straightforward
	case reflect.Float64:
		{
			ptr := new(float64)
			*ptr = L.ToNumber(idx)
			value = *ptr
		}
	case reflect.Float32:
		{
			ptr := new(float32)
			*ptr = float32(L.ToNumber(idx))
			value = *ptr
		}
	case reflect.Int:
		{
			ptr := new(int)
			*ptr = int(L.ToNumber(idx))
			value = *ptr
		}
	case reflect.Int8:
		{
			ptr := new(byte)
			*ptr = byte(L.ToNumber(idx))
			value = *ptr
		}
	case reflect.String:
		{
			tos := L.ToString(idx)
			ptr := new(string)
			*ptr = tos
			value = *ptr
		}
	case reflect.Bool:
		{
			ptr := new(bool)
			*ptr = bool(L.ToBoolean(idx))
			value = *ptr
		}
	case reflect.Slice:
		{
			// if we get a table, then copy its values to a new slice
			if L.IsTable(idx) {
				value = CopyTableToSlice(L, t, idx)
			} else {
				value = unwrapProxy(L, idx)
			}
		}
	case reflect.Map:
		{
			if L.IsTable(idx) {
				value = CopyTableToMap(L, t, idx)
			} else {
				value = unwrapProxy(L, idx)
			}
		}
	case reflect.Func:
		{
			if L.IsFunction(idx) {
				value = LuaGoFunc(L, t, idx)
			}
		}
	case reflect.Interface:
		{
			if L.IsTable(idx) {
				// have to make an executive decision here: tables with non-zero
				// length are assumed to be slices!
				if L.ObjLen(idx) > 0 {
					value = CopyTableToSlice(L, nil, idx)
				} else {
					value = CopyTableToMap(L, nil, idx)
				}
			} else if L.IsNumber(idx) {
				value = L.ToNumber(idx)
			} else if L.IsString(idx) {
				value = L.ToString(idx)
			} else if L.IsBoolean(idx) {
				value = L.ToBoolean(idx)
			} else {
				value = unwrapProxy(L, idx)
			}
		}
	default:
		{
			fmt.Println("unhandled type", t)
			value = 20
		}

	}
	return value

}